This invention relates to systems for maintenance of complex systems and more specifically methods and apparatus for associating fault models and deferral procedures using historical data related to such systems.
Complex systems comprising tens or hundreds of inter-related and inter-operating systems and subsystems, many which may be complex in there own right, present unique maintenance and service challenges. Examples of such complex systems include factories, major buildings, ocean-going vessels, power generation plants, and aircraft to name a few. Complex systems and the inter-related and inter-operational nature of the systems and subsystems thereof often require equally complex and disciplined maintenance and service programs. These programs usually include documentation or records of observed or indicated irregularities or discrepancies and actions taken or services performed pursuant to resolution or prevention of such irregularities and discrepancies. This documentation is usually filled out, completed, or recorded by service and maintenance personnel. Expert systems and tools that can standardize service and maintenance diagnoses, procedures, cost estimates and so on are highly desirable for the time savings and precision they can offer to an overall maintenance and operational support program.
In the aircraft industry fault codes have more recently come to be used to provide a mechanism to summarize the set of symptoms or syndrome that is reported for each distinct aircraft fault condition. A fault code typically corresponds to a fault condition in a single system on the aircraft and can be used as the basis of fault isolation, material planning and deferral/criticality analysis. Fault Codes are a critical element of a xe2x80x9cFault Modelxe2x80x9d for an aircraft that can be used to support an automated diagnostic and maintenance support system. Deferral Procedures for an aircraft, for example, identify the set of fault conditions for which that aircraft can still be safely operated. These procedures are typically recorded in the aircraft xe2x80x9cMinimum Equipment Listxe2x80x9d (MEL) which is supplied by or derived from a list supplied by the aircraft manufacturer.
Honeywell International Inc. builds an automated expert system called xe2x80x9cAMOSSxe2x80x9d (Aircraft Maintenance and Operations Support System) that uses fault codes as a standard element in structuring the maintenance activities for an airline and aircraft within that airline. This system also assists airline personnel in the determination of which Deferral Procedures are appropriate for a given fault condition. Airlines and other suppliers also build similar systems with some of this functionality. In order to provide this functionality, it is critical that the system records a linkage or association between system fault conditions, as represented through Fault Codes, and the Deferral Procedures that are relevant. Historically this linkage could only be derived through manual generation of the data for this relationship. This is a very time consuming and error prone activity that adds complexity to the maintenance and service procedures, increases costs, and reduces the precision of planning and cost analysis activities. Clearly a need exists for methods and apparatus for associating deferral procedures and standard fault codes based on historical data.
The instant invention in overview is a method of associating deferral procedures to a fault model for complex systems based on historical data. The method includes: analyzing the historical data for deferral information to identify a plurality of deferral procedures; associating each of the plurality of deferral procedures with a corresponding one or more of a plurality of standard repairs; linking each of the plurality of standard repairs with a fault code; and associating each of the plurality of deferral procedures with one or more of the fault codes that were linked, respectively, with the one or more of the plurality of standard repairs to thereby provide a set of associations between the plurality of deferral procedures and a plurality of fault codes.
Preferably, analyzing the historical data for deferral information to identify the plurality of deferral procedures further includes assigning a deferral procedure from a deferral procedure list to each occurrence of deferral information. Also a reference to the historical data may be maintained with each of the plurality of deferral procedures and each of the plurality of standard repairs. The process of associating the plurality of deferral procedures preferably further includes creating relationships between the plurality of deferral procedures and the plurality of standard repairs utilizing the historical data that is common between a deferral procedure and a standard repair. The act of linking the plurality of standard repairs likely includes selecting the fault code from a standard fault code list. The method may also include reviewing and accepting a portion of the set of associations. In a preferred form this method is used to associate deferral procedures to a fault model for an aircraft.
One aspect of the invention is a software program comprising software instructions that are arranged to run on a processor to process information derived from historical data in order to facilitate associating deferral procedures to a fault model for complex systems based on the historical data. The software program when installed and operating on a processor results in the processor performing the method. Another aspect of the invention is a computer based aircraft maintenance and operations support system for automatically associating deferral procedures with an aircraft fault model based on historical data when the computer is executing the software program to perform the above reviewed method.